Mayor John Cranley is apologizing to police leaders after his office mistakenly named a day for the man who killed Cincinnati police officer Sonny Kim.

A staffer on Thursday approved a proclamation declaring June 1 as “Tre Day” in honor of Trepierre Hummons.

Hummons gunned down Kim, a veteran CPD officer, on a Madisonville street in June 2015.

Hummons’ father, Ronald, submitted the proclamation request and posted images of the certificate on Facebook Thursday.

The certificate is stamped with Cranley’s signature and claims in-part that Trepierre’s “sacrifice will save the lives of children for generations to come.”

A tearful Cranley apologized Thursday night in a press conference at the police union hall.

He called the situation "a huge mistake."

"Both staff members who reviewed the proclamation were not in my office nor worked for the city of Cincinnati when Officer Kim was murdered," Cranley wrote in an apology letter to FOP President Dan Hils.

"They were both unaware that TrePierre was the man who murdered Sonny Kim."

Cranley, who was visibly emotional, said he never reviewed the proclamation.

"I am sorry that my office, that we mistakenly issued a proclamation on behalf of a man that killed, murdered Sonny Kim," he said tearfully.

"It wasn't anything specific about this person's background, and I was not aware, and it's my fault, and I'm sorry," Holly Stutz Smith said.

The mayor sent an official retraction to Hummons' father and called Kim's wife, Jessica, to apologize.

"I've walked with him. I've rode with them. I would never do anything to hurt," Cranley said.

Cincinnati Police Specialist Tom Sandmann, who Trepierre Hummons shot at when he responded to Officer Kim's shooting before he even got out of his police SUV, said he spoke with the mayor Thursday, and Cranley apologized to him as well.

Specialist Sandmann returned fire in self-defense and shot and killed Hummons after Hummons shot Officer Kim.

The police union leader said Thursday he believes this opens up a lot of wounds across the police force, but he's hopeful in this case, history won't repeat itself.

"I don't blame John Cranley personally. I do fault something with the operations in the mayor's office," he said.

Cranley vowed it wouldn't happen again.

Linda Pope, the wife of Officer Daniel Pope, who was fatally shot by a wanted suspect in the line of duty on Dec. 5 1997 along with Specialist Ron Jeter, is the keynote speaker at Friday's annual Police Memorial Week ceremony and march Downtown.

She released a statement to FOX19 NOW late Thursday, saying she understands mistakes happen.

"Well they certainly seem distraught by this. An error was made. People are human and it seems legit to me their sincerity," she wrote.

"As long as Jessica Kim has been apologized to and the proclamation has been rescinded, I am OK with the mistake. No one needs to lose their job in my opinion. Total human error. I hope they are more careful in the future before they make such proclamations. I am happy they contacted Dan Hill as quickly as they did."

Hummons killed Officer Kim, a veteran officer, on the rainy morning of June 19, 2015.

Hamilton County Prosecutor Joe Deters has described the the shooting as an "evil ambush."

"His goal was to lure and kill as many police officers as he could," Deters told reporters in a December 2015 press conference when he released police cruiser video of the shooting. "His intention was mass murder."

Hummons called 911 on himself twice in a plan for ‘suicide by cop.’ He reported an armed man acting belligerently at Whetsel Avenue and Roe Street.

When Officer Kim responded to the scene, Hummons began firing at the 27-year veteran of the department.

Both were rushed to University of Cincinnati Medical Center, where they died.

Hummons, who was connected to the neighborhood Clutch Gang, sent text messages and posted to Facebook indicating he planned suicide by cop.